Cutting implement for flat-bed sewing machine

ABSTRACT

A sewing machine, used for stitching slide fasteners to garments or other pieces of fabric, has a fixed cutter blade spacedly positioned above the machine bed downstream of a pair of stitching needles and a coacting movable cutter blade carried on a vertically reciprocable slider normally withdrawn below the bed surface. The slider, upon being elevated during the cutting step, intercepts an overlying fastener section and clamps it against a spring-loaded shoe overhanging the bed. The clamped section, immediately after being severed from an adjoining section, is contacted by a welding tool fusing some of its links into a bottom stop.

1451 Dec. 31, 1974 CUTTING IMPLEMENT FOR FLAT-BED SEWING MACHINE 1 [76]Inventor: Ruggero Dal Negro, Via Cusani 10,v

Milan, Italy [22] Filed: Apr. 15, 1974 [21] App]. No.: 461,144

[30] Foreign Application Priority Data Apr. 19, 1973 Italy 23176/73 [56]References Cited UNITED STATES PATENTS 4/1952 Phillips 112/130 X '4/1966Steingruebner 1 12/130 X 11/1969 Adams 112/130 X 3,709,758 l/l973Gilmore 156/580 X 3,770,552 1l/l973 Lacam 156/580 X Primary Examinerl-l.Hampton Hunter Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno 7]ABSTRACT A sewing machine, used for stitching slide fasteners togarments or other pieces of fabric, has a fixed cutter blade spacedlypositioned above the machine bed downstream of a pair of stitchingneedles and a coacting movable cutter blade carried on a verticallyreciprocable slider normally withdrawn below the bed surface. Theslider, upon being elevated during the cutting step, intercepts anoverlying fastener section and clamps it against a spring-loaded shoeoverhanging the bed. The clamped section, immediately after beingsevered from an adjoining section, is contacted by a welding tool fusingsome of its links into a bottom stop.

i 9 Claims, 2 Drawing Figures CUTTING IMPLEMENT FOR FLAT-BED SEWINGMACHINE FIELD OF THE INVENTION My present invention relates to a cuttingimplement for a sewing machine of the flat-bed type, more particularly amachine used to stitch slide fasteners to garments or other pieces offabric.

BACKGROUND OF THE INVENTION stantially matches that of the slit or edgealong which the fastener is attached to the workpiece. Conventionalshear-type cutters used for this purpose, with relatively movable upperand lower blades, produce a neat cut but are difficult to install onsuch a machine without interfering with either the advance of theworkpiece and the fastener in the stitching direction or the operativepositioning of each new workpiece preparatorily to the sewing ofafastener section thereto. The alternative solution of a chopping cut, inwhich a single blade strikes from above against an underlying anvil,entails a less clean severance of the fastener sections and alsonecessitates frequent replacements of the cutter blade because of rapidwear.

OBJECTS OF THE INVENTION The general object of my present invention,therefore, is to provide in such a machine a shear-type cuttingimplement which, while idle, allows the workpiece and the slide fastenerto travel along a virtually unobstructed path over the upper surface ofthe machine bed.

Another object is to provide means associated with such a cuttingimplement for forming an end stop in an oncoming fastener sectionsimultaneously with the severance of the preceding section therefrom.

SUMMARY OF THE INVENTION In accordance with my present invention, thecutting implement comprises a fixed cutter blade specedly disposed abovethe gap of the bed downstream of the needles and a movable cutter bladeconfronting the fixed blade in operative alignment therewith, thismovable blade being mounted on a support which is normally withdrawnbelow the bed surface. A preferably fluidic actuator is operable toelevate the support together with the movable blade for coaction withthe fixed blade at the end ofa stitching operation, thereby severing afastener section previously sewn onto a workpiece from an adjoiningsection overlying the gap.

Advantageously, pursuant toa'further feature of my invention, aspring-loaded shoe overhangs the gap above the elevatable supportbetween the fixed blade and the needles, the bottom surface of this shoebeing normally disposed below the level of the cutting edge of the fixedblade for upward entrainment by the rising support. Thus, the overlyingfastener section is clamped between the shoe and the support even as theimmediately preceding section is being severed therefrom. A weldingtool, preferably a supersonic vibrator, is fixedly disposed above thebed for contact with the clamped fastener section, this tool having afastenerengaging point which lies above the level of the cutting edge ofthe fixed upper blade and contacts the clamped section in order to forman end stop thereon by a fusion of some of its links as is well knownper se.

According to another feature of my invention, the cutting edge of themovable lower blade is normally (i.e., in the withdrawn positionthereof) about flush with the upper bed surface so as to minimize thelength of its cutting stroke. This movable cutter'blade is preferablychamfered in such a manner that a land adjoining its cutting edgesslopes downwardly from that edge toward the needles so as to act as atemporary support for the free end of the clamped fastener section,guiding this free end onto the clamping.

BRIEF DESCRIPTION OF THE'DRAWING SPECIFIC DESCRIPTION In the drawing Ihave shown a sewingmachine l with a frame 16 rising from a bed 3, themachine being provided with a-pair of laterally juxtaposed needles 2(only one shown) which are aligned with a longitudinal gap 3"in the bed3. The gap 3', which need not be continuous as shown but could also belongitudinally subdivided, is partly occupied by a conventional needleplate 33 having openings 34 for passage of the needles 2. Plate 33 alsohas a longitudinal groove 33' (FIG. 2) for positive lateral guidance ofa slide fastener 31 to be stitched onto an overlying workpiece 32 suchas a slitted skirt. The machine also includes such nonillustratedconventional elements as an underthread-handling mechanism and a feederfor the advancement of the cloth in the direction of arrow F, i.e., fromright to left,

along with ancillary equipment such as a tension regulator for threads35 passing through the needle tips and an alarm device designed tosignal a thread rupture.

A presser foot 24 is mounted on the lower end of a vertically movable,conventionally spring-loaded stem 23 which projects downwardly from theframe 16 and can be manually raised or lowered in the usual manner. Alug 25 secured to that stem is traversed by a pair of parallelverticalpins 26 (only one shown) which are surrounded by springs 30 and haveheads 29 limiting their descent relative to the lug 25. A shoe 27 isscrewed onto the lower ends of the pins 26 and normally lies slightlyabove the upper surface of bed 3 so as to give' passage to a fastener 31and an overlying workpiece 32 advancing during a stitching operationbetween the bed and the presser foot 24. Shoe 27 has a hole 28 alignedwith the tip of a welding tool 20 which is actuatable by a supersonicvibrator 19 carried on an extension 18 of frame 16, this extension beingsecured upper bed surface upon'untor sitting at the right of the machine1, so that its tip normally clears the shoe 27. Frame extension 18 alsocarries a mounting 21 for a cutter blade 22 whose cutting edge 22 liesat a fixed distance above the bed 3, at a level below the tip of tool 20but above the underside of shoe 27 in the illustrated normal positionthereof.

.Shoe 27 confronts a slider 13 which supports a movable cutter blade 15co-operating with the fixed blade 22. Blade 15 has a cutting edge 15'adjoining a beveled land 15" which slopes downwardly from that edgetoward the right, i.e., in the direction of the needles 2 and themachine operator. Land 15" terminates at the level of the upper surfaceof slider 13 which has a recess 14 accommodating the shoe 27 when theslider is raised, together withblade 15, above the bed surface in orderto sever the fastener 31 between blades 15 and 22. The verticalreciprocation of slider 13,'which forms part of a movable blade support11, is controlled by an actuating mechanism 4 comprising a double-actingpneumatic jack 9' whose piston rod 9 is articulated at 8 to an extremity5' of a lever 5 having its other extremity 5".received in a cutout ofslider 13 which is guided in a stationary casing 12 secured to themachine frame. Lever 5 is fulcrumed at 6 on a bracket 7 depending frombed 3.

In operation, presser foot 24 is lifted together with lug 25 andshoe 27to provide clearance for the workpiece 32,such as a slitted skirt, whichis placed atop the bed 3 above the fastener 31 with the open end of theslit facing toward the operator. Next, the workpiece is pulled by theoperator against the direction of arrow F, i.e., to theright, until theclosed end of the slit comes to lie against thethreads 35 depending fromthe needles 2. The presser foot 24 isnow lowered so that the partsassume the position shown in FIG. 1. With the aid of the feedingmechanism, or possibly under manual pressure, the garment 32 and-theslide fastener 31 are moved to the left (arrow F) while beingchain-stitched to each other through the turns of the coiled fastenerhalves as is well known per se; the fastener halves may be occupied forthis purpose by respective cords substantially heavier than the threads35. When the garment 32 has cleared the cutting. zone, as illustrated inFIG. 2, a pushbutton or the like is operated to pressurize the jack 9 soas to force the piston rod 9 downwardly, arrow H, whereby the lever 5swings counterclockwise and elevates the slider 13 with its movablecutting blade 15 to sever a fastener section 31a, previously stitchedonto the garment 32, from the remainder of the fastener 31. During thisupward movement another fastener section 31b. overlying the gap 3between the slider 13 and the shoe 27,-is firmly clamped between thesetwo elements as the shoe 27 comes to rest within the recess 14 of slider13. Immediately after the severance, i.e., as the clamped fastenersection 31b, rises above the level of cutting edge 22' against the forceof springs 30, this section is contacted by the welding tool which fusesa few of its links into an end stop, namely a bottom stop for the lengthof fastener to be sewn onto the next workpiece. Via spring 30, actingupon lug 25, the presser foot 24 may also be raised at this time (to alesser extent than shoe 27) against the force of its loading spring.

After the slider 13 has been held elevated for the time necessary toform this bottom stop, the operation of jack 9' is reversed to restorethe normal position of the parts. At this point the free end of fastenersection 31b rests on the land 15" of cutter 15 so as to be deflectedupwardly, onto the adjoining bed surface, im mediately upon resumptionof the leftward advance of the fastener after a new workpiece has beenplaced upon the same in the aforedescribed manner.

Naturally, the tool 20 is'representative of a variety of welding devicesthat could be used for fusing the fastener links to form an end stop.The use ofa supersonic vibrator, however, is preferred since it avoidsthe need for high temperatures which could be dangerous to the machineoperator.

I claim:

1. In a sewing machine for slide fasteners comprising a flatbed providedwith a gap and ,a pair of parallelneedles aligned with said gap forstraddling two interlinked slide-fastener halves while stitching sameonto a workpiece moving along said bed, the combination therewith of: I

a fixed cutter blade spacedly disposed above said gap downstreamvof saidneedles;

a movable cutter blade confronting said fixed blade in operativealignment therewith;

a support for said movable blade normally withdrawn below the uppersurface of said bed;

actuating means operable to elevate said-support together with saidmovable blade through said gap for coaction with said fixed blade tosever a slidefastener section overlying said gap from an adjoiningsection; and a spring-loaded shoe overhanging said gap above saidsupport between said fixed blade and said needles, said shoe having abottom surface normally disposed below the level of a cutting edge ofsaid fixed blade but elevatable above said level upon entrainment by Isaid support whereby said overlying section is clamped between said shoeand said support.

2. The combination defined in claim 1 wherein said support has an upperface with a recess accommodating said shoe.

3. The combination defined in claim 1, further comprising welding meansfixedly disposed'above said bed for contact with a slide-fastenersection clamped between said support and said shoe upon elevationthereof to fuse part of the clamped section into an end stop, saidwelding means having a fastener-engaging point lying above the level ofsaid cutting edge.

4. The combination defined in claim 1, further comprising aspring-loaded presser foot disposed upstream of said shoe in thevicinity of said needles, further comprising a holder for said shoesecured to said presser foot and guide means mounting said shoe on saidholder wit limited relative vertical mobility.

5. The combination defined in claim 1 wherein said shoe has a'cutoutpenetrated by said fastener-engaging point upon elevation of said shoe.

6. The combination defined in claim 3 wherein said welding meanscomprises a supersonic vibrator.

7. The combination defined in claim 1 wherein said actuating meanscomprises a fluid-operated piston.

8. The combination defined in claim 1 wherein said movable blade has acutting edge normally lying sub-

1. In a sewing machine for slide fasteners comprising a flat bedprovided with a gap and a pair of parallel needles aligned with said gapfor straddling two interlinked slide-fastener halves while stitchingsame onto a workpiece moving along said bed, the combination therewithof: a fixed cutter blade spacedly disposed above said gap downstream ofsaid needles; a movable cutter blade confronting said fixed blade inoperative alignment therewith; a support for said movable blade normallywithdrawn below the upper surface of said bed; actuating means operableto elevate said support together with said movable blade through saidgap for coaction with said fixed blade to sever a slide-fastener sectionoverlying said gap from an adjoining section; and a spring-loaded shoeoverhanging said gap above said support between said fixed blade andsaid needles, said shoe having a bottom surface normally disposed belowthe level of a cutting edge of said fixed blade but elevatable abovesaid level upon entrainment by said support whereby said overlyingsection is clamped between said shoe and said support.
 2. Thecombination defined in claim 1 wherein said support has an upper facewith a recess accommodating said shoe.
 3. The combination defined inclaim 1, further comprising welding means fixedly disposed above saidbed for contact with a slide-fastener section clamped between saidsupport and said shoe upon elevation thereof to fuse part of the clampedsection into an end stop, said welding means having a fastener-engagingpoint lying above the level of said cutting edge.
 4. The combinationdefined in claim 1, further comprising a spring-loaded presser footdisposed upstream of said shoe in the vicinity of said needles, furthercomprising a holder for said shoe secured to said presser foot and guidemeans mounting said shoe on said holder wit limited relative verticalmobility.
 5. The combination defined in claim 1 wherein said shoe has acutout penetrated by said fastener-engaging point upon elevation of saidshoe.
 6. The combination defined in claim 3 wherein said welding meanscomprises a supersonic vibrator.
 7. The combination defined in claim 1wherein said actuating means comprises a fluid-operated piston.
 8. Thecombination defined in claim 1 wherein said movable blade has a cuttingedge normally lying substantially at the level of said upper surface. 9.The combination defined in claim 8 wherein said movable blade ischamfered with a land sloping downwardly from the cutting edge thereoftoward said needles.